Device for Recycling Grey Water in a Transportation Vehicle

ABSTRACT

The invention pertains to a device (C) for recycling grey water, particularly for a transportation vehicle equipped with a tank (D) of clean on-board water, said device (C) being intended for providing recycled water for the emptying of at least one toilet mounted in said vehicle, said device comprising a vessel ( 2 ) for collecting grey water, a pump ( 4 ) to make at least at a part of the grey water stored in the vessel ( 2 ) circulate towards filtering means ( 8 ) and a tank ( 12 ) for storing filtered grey water useable for washing the toilets. said filtered grey water being stored under pressure in said tank ( 12 ). 
     According to the invention, said filtering means ( 8 ) comprise an ultrafilter.

1. FIELD OF THE INVENTION

The field of the invention is that of the treatment of water in transportation vehicles, especially but not exclusively, in an aircraft.

More specifically, the invention pertains to a technique for recycling grey water in a transportation vehicle of this kind.

2. PRIOR ART

There is a particularly high demand in air transport for solutions to limit the consumption of fuel needed for aircraft flight so as to reduce costs.

The constraints of weight on apparatuses in aircraft, especially apparatuses requiring the use of on-board water, are therefore high.

On board the aircraft, potable water is stored in one or more tanks and is generally intended for pressurized supply to toilet flushes, wash-basins and galleys.

In certain aircraft, the grey water coming from the wash-basins and the galleys are discharged out of the aircraft by one or more drainmasts (the term “grey water” refers to water with low pollutant content resulting from dishwashing, hand washing and showers).

Since the volume of water taken on board an aircraft is limited, solutions have been proposed for recycling grey water.

Thus, there are known ways of recycling grey water in wash-basins in order to flush out toilets.

However, these prior-art devices have a certain number of drawbacks in that they are complicated devices implementing numerous pumps, valves, filters and water pipes that especially require much space and intensive maintenance, and are relatively heavy.

Besides, it is well known that the space needed for the passage of the pipes of the water circuits in an aircraft is extremely limited. The water circuits generally pass beneath the floors of the aircraft cabin and, in the event of leakage or malfunction, they necessitate lengthy and costly dismantling operations. This causes the aircraft to be grounded.

3. GOALS OF THE INVENTION

The invention is aimed especially at overcoming these drawbacks of the prior art.

More specifically, it is a goal of the invention to provide a device for recycling grey water in a transportation vehicle, especially an aircraft (for example a commercial aircraft) intended for supplying water to the flush system of a toilet and meeting the constraints dictated by air transport, namely:

-   -   the weight of the device must be minimal because any excess         weight leads to excess consumption of energy by the aircraft,         and its space requirement has to be limited,     -   maintenance has to be minimal and must be integrated into the         aircraft maintenance plans,     -   the water system has to be drainable without electricity when         the aircraft is at a halt (i.e. once the electrical power supply         to the aircraft is cut off),     -   the flushing of the toilets has to be optimal (with no smells,         residues or colors) whether it is done with recycled water or         with on-board potable water, and     -   the quantity of water to be taken on board has to be minimal

It is another goal of the invention to provide a recycling device of this kind that prevents any contamination of the on-board water system and can be bypassed, in the event of malfunction for example, without harming the operation of the toilet (in other words, it must remain possible to supply flushing water to the toilet even when the recycling device is deactivated).

4. SUMMARY OF THE INVENTION

These goals as well as others that shall appear more clearly here below are achieved by means of a device for recycling grey water, particularly for a transportation vehicle equipped with a tank of clean on-board water, said device being intended for providing recycled water for the emptying of at least one toilet mounted in said vehicle, said device comprising a vessel for collecting grey water, a pump to make at least at a part of the grey water stored in the vessel circulate towards filtering means and a tank for storing filtered grey water useable for washing the toilets, said filtered grey water being stored under pressure in said tank.

According to the invention, said filtering means comprise an ultrafilter. Thus, the invention relies on a wholly original approach to the recycling of grey water in a transportation vehicle, and especially in an aircraft, that uses the water flowing from a wash-basin (hand-sink) or a shower of the aircraft as toilet-flushing water.

The retrieved water, known as grey water, is filtered by an ultrafilter and stored under pressure, and not under atmospheric pressure, in a cylinder.

The use of such a filter enables the production of filtered water, the quality of which is acceptable for use in toilet flushes.

The ultrafilter makes it possible especially to eliminate the organic matter, bacteria and colors from the grey water which is intended, once filtered, for the flushing of toilet bowls.

According to one advantageous characteristic of the invention, said filtered grey water is stored in said tank at a pressure of 2 to 4 bars.

The grey water filtered by the ultrafilter is stored under pressure in a cylinder at a pressure of 3.5 bars for example, and not under atmospheric pressure. This technique is advantageous in that the pressurizing of the flushing water upstream to the toilet bowl does not require the use of a pump to draw out the filtered water and direct it towards the toilet bowl. A pump of this kind would however be necessary if the filtered grey water were to be stored in the cylinder at atmospheric pressure.

Thus, the device of the invention is economical, light and compact.

Furthermore, the maintenance of such a device is reduced and relatively easy.

The invention provides a structural solution that is simple, silent and minimizes the volume of storage of the potable water and the wastewater (and therefore reduces the weight carried during the flight of the aircraft) and meets safety requirements, especially in the field of air transport.

It can also be noted that it is contrary to the practice of those skilled in the art to apply pressure downstream to an ultrafilter. Indeed, the pressure downstream to a filter is generally minimized in order to maximize the transmembrane pressure on the one hand and prevent jerky operation (due to high pressure upstream and downstream) on the other hand.

In addition, in the event of a backwashing of an ultrafilter, it is particularly inadvisable to apply pressure downstream to the filter.

The fact of applying pressure of 2 to 4 bars downstream to the ultrafilter in the device of the invention thus constitutes a solution that runs counter to preconceived ideas.

Advantageously, the recycling device comprises a valve to selectively connect said toilet to the filtered grey-water storage tank or to said on-board clean-water tank.

A device of this kind can be deactivated and bypassed in the event of problems. Thus, the toilet remains functional even in the event of malfunctioning of the recycling device, the flushing water for the toilet bowl being provided by the on-board potable water system (it is therefore possible to have an operation without recycling of the grey water of the aircraft water system).

Preferably, the recycling device comprises a non-return clack valve between said on-board clean water tank and said valve.

The device of the invention is provided with an anti-return safety device preventing a return towards the potable water system of the vehicle and is therefore independent of the on-board potable water system of the vehicle.

Thus, the return of grey water and/or recycled water towards the potable water tank is made impossible.

In other words, a clack valve of this kind is aimed at preventing the circulation of filtered grey water towards the on-board clean water tank.

Advantageously, the recycling device comprises a back-pressure valve between said valve and the grey-water collecting vessel.

A back-pressure valve of this kind is aimed at maintaining stable pressure in the filtered water tank and therefore at improving the precision of the dosing of filtered grey water that can be used for washing toilets and also for securing the filtered grey water circuit in preventing any excess pressure in the circuit.

Advantageously, said recycling device comprises pressure sensors placed respectively upstream and downstream relative to the filtering means so as to determine the difference in pressure between the inlet and the outlet of the filtering means.

This difference in pressure is used to indicate any clogging, even a partial clogging, of the grey-water filter which could harm the quality of the toilet-flushing water.

It therefore indicates that an operation of maintenance of the filter (cleaning or replacement) is necessary.

Preferably, said recycling device comprises a sensor of the level of filling of the grey-water collector vessel.

The output signal of such a sensor can be used to determine the quantity of water available to flush out the toilets and anticipate a possible lack of recycled water, which would make it necessary to bypass the recycling circuit to flush out the toilets with on-board clean water.

Advantageously, said recycling device is connected to electronic control and command means.

These electronic control and command means of the device of the invention take the form of a microcontroller for example which receives the data measured by the different sensors of the device and delivers the command signals for the device.

Preferably, said electronic control and command means comprise means to command the starting or stopping of said recycling device.

According to one advantageous characteristic of the invention, said electronic control and command means include means commanding the backwashing of the filtering means with filtered grey water stored in said tank.

The backwashing of the filtering means with filtered grey water stored in the tank is advantageous in that it does not require the use of chemicals.

According to one advantageous characteristic of the invention, to command the backwashing of the filtering means, said electronic control and command means take account of at least one of the following criteria:

-   -   a predetermined duration of operation of the filtering means;     -   a predetermined loss of load through the filtering means;     -   a volume of water filtered by the filtering means;     -   a clock signal;     -   output signals from the pressure sensors;     -   a water flow-rate signal.

The backwashing can be clock-activated (i.e. activated at predetermined time intervals) or else when a clogging of the grey water filter is detected through output signals from the pressure sensors situated upstream and downstream from the filter (and/or from flow-rate signals).

It can also be triggered according to a duration of operation of the filter and/or a predetermined loss of load and/or a volume of water filtered by the filter.

Advantageously, said electronic control and command means include means that command the emptying of said recycling device and implement said pump.

Thus, the device of the invention is entirely and automatically drainable. Such a maintenance operation is relatively easy.

According to one advantageous characteristic of the invention, said electronic control and command means include means activating the draining of the matter in suspension from the grey water retained by the filtering means.

Such a draining of matter in suspension can be implemented when a backwashing of the grey-water filter is in progress or else is terminated.

Advantageously, said recycling means include means of reversible fastening to a toilet module comprising a wash-basin and a toilet.

Preferably, it comprises means for linking the grey-water collecting vessel to a wash-basin or to a shower mounted in said vehicle.

The device of the invention is decentralized and installed for each toilet module of an aircraft for example, in the passenger space. It is advantageous in that it takes up no volume in the hold of the aircraft.

It is compact (i.e. it has low space requirement, which is very important for aircraft especially) and it is easy to mount and dismount.

Toilets equipped with said device offer an efficient compromise between passenger comfort and operational cost for airlines.

5. LIST OF FIGURES

Other features and advantages of the invention shall appear more clearly from the following description of a particular embodiment of the invention given by way of a simple illustratory and non-exhaustive example and from the appended FIG. 1 which is a schematic representation of the device for recycling grey water according to the invention according to one embodiment.

6. DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

By way of an example, a description is given here below of the working of the grey-water recycling device of the invention when it is implemented in an aircraft (a commercial aircraft for example).

It can be understood nevertheless that this device can be implemented in other vehicles, for example camping cars, trains, ships and buses.

In the example illustrated schematically in FIG. 1, each toilet module of the aircraft has a wash-basin or hand-sink A, the tap of which is connected by a pipe L6 to a tank D of on-board potable water, and a toilet bowl B which is connected to a tub for storing wastewater (not shown).

Each fitting furthermore comprises a recycling device or unit C to filter grey water flowing from the wash-basin A and supplying the flush system of the toilet B with this filtered water.

Unlike in prior-art solutions which implement a centralized recycling device, i.e. only one recycling unit for the entire aircraft, the recycling unit C is in this case decentralized. In other words, each module of the toilets of an aircraft is fitted out with a dedicated recycling unit.

The use of such a decentralized recycling unit C minimizes the number of pipes, and therefore the weight, necessarily implemented in a centralized device to connect this device to the different monuments of the aircraft. This aspect is important since, as emphasized here above, the space used for the passage of the pipes in the plane is extremely constricted.

The recycling unit C implemented in each toilet module of the aircraft is thus placed between the wash-basin A and the toilet bowl B. It comprises a vessel 2 for receiving grey water, a pump 4 to make the grey water of the vessel 2 flow towards a grey-water ultrafiltration module 8 and an expansion vessel 12 for pressurizing the grey water filtered by the ultrafiltration module 8.

These different elements 2, 4, 8, 12, A, B, C are connected to one another by pipes or conduits represented schematically in FIG. 1 by lines.

The vessel or reservoir 2 has a capacity of about four liters in this example, and enables the storage of grey water flowing from the wash-basin B through the conduit L1.

The wash-basin A is supplied with clean water from the tank D of on-board water by means of the conduit L6. The vessel 2 is provided with a filling-level sensor 3, the output signal of which is sent to a microcontroller of a control and command device, or central processing unit E, thus making it possible to have an indication of the level of filling of the vessel 2.

It can be noted that a three-way valve 1 is provided. This three-way valve 1 is placed between the wash-basin A and the vessel 2, and is designed to make the grey water coming from the wash-basin A circulate either towards the vessel 2 or towards a removal device or drainmast when the vessel 2 is full or when the recycling unit C is deactivated. The valve 1 is, like the other valves of the recycling unit C, a solenoid valve in this example.

The pump 4 which, in this example, is a self-priming pump provided with a pressure switch and designed to obtain the circulation of at least one part of the grey water which is stored in the vessel 2 towards the ultrafiltration module 8 through the conduit L2.

Between the pump 4 and the ultrafiltration module 8, there are provided respectively a non-return clack valve 5 and a flowmeter 6 used to measure the flow rate of the water circulating in the conduit L2 (and therefore the flow rate of the pump 4).

Classically, the ultrafiltration module 8 has a filtering chamber (not shown) comprising a semi-permeable membrane which separates the internal volume of the ultrafiltration chamber into two compartments: the compartment that receives the grey water to be filtered and the compartment that receives the filtered water.

The filter or filtering membrane (not shown in FIG. 1) implemented in the ultrafiltration module 8 enables an optimized reduction of the matter in suspension in the grey water coming from the vessel 2 as well as partial but sufficient reduction of the color and organic matter in this grey water (and therefore a reduction of olfactory nuisance).

The liquid filtered by the ultrafiltration module 8 and coming out of this module 8 through the conduit L3 is herein called a filtrate and the matter blocked by the ultrafiltration module 8 is called concentrate.

The ultrafiltration module 8 enables the filtering of 120 liters per hour of grey water under pressure of 1.3 bars or 19 psi (pound per square inch). It is connected to a first valve 10 with two channels for emptying the ultrafiltration module 8, such a emptying being implemented when the aircraft is at a halt for example. The valve 10 is connected to a conduit L8 which itself is connected to the drainmast.

The ultrafiltration module 8 is furthermore connected to a second valve 11 with two channels for discharging concentrates resulting from the ultrafiltration towards the drainmast. The valve 11 is connected to a conduit L8 which itself is connected to the drainmast.

Besides, the ultrafiltration module 8 is connected to two pressure sensors 7 and 9 respectively situated upstream and downstream with respect to the ultrafiltration module 8 on the conduits L2 and L3 respectively. The sensors 7 and 9, which are electronic sensors of a known type, are used to determine the difference in pressure between the inlet and outlet of the ultrafiltration module 8 and thus detect any possible clogging of the filter of the ultrafiltration module 8.

Should the ultrafiltration module 8 be clogged (in this example, the transmembrane pressure measured by the two pressure sensors 7 and 9 is greater than 1 bar for example), an alarm (not shown) gets activated. In this case, the toilet returns to operation without recycling and remains functional.

It must be noted that the use of pressure sensors 7 and 9 makes it possible not only to track the progress of the transmembrane pressures of the ultrafiltration module 8 and anticipate the clogging of the filter but also to fine tune the volume of water to be taken aboard before each take-off by the aircraft. This therefore optimizes the weight taken on board the aircraft.

Besides, the recycling unit 6 implements an expansion vessel 12 comprising means for the pressurizing (in this example, with a pressure of 45 psi or 3.1 bars) of a predetermined volume of filtered water (or filtrate) by the ultrafiltration module 8.

More generally, the filtered grey water is stored in the expansion vessel 12 at a pressure of 2 to 4 bars, for example at a pressure 2, 5 to 4 bars, or 3 to 4 bars in another example

The filtered water stored in the expansion vessel 12 is intended for flushing the bowl of the toilets B via the conduit L4. The volume of water stored under pressure in the expansion vessel 12 is for example 600 milliliters, a volume equivalent to about three toilet flushings.

The expansion vessel 12 thus constitutes a reservoir of flushing water sized so as to be able to store several volumes of flushing water which can be supplied to the toilets successively without the pump 4 being primed.

The cleaning of the vessel is for example activated by the user by means of a handle or button. The flushing water is delivered into the vessel by any type of device known to those skilled in the art.

The storage of the filtrate under pressure in the expansion vessel 12 prevents the use of a storage tank for the filtrate at atmospheric pressure and the use of a pump for sending the filtrate thus stored towards the toilets.

The solution of the invention thus restricts the number of elements needed for recycling grey water and therefore the weight and cost of the recycling device C. It also reduces maintenance operations.

The expansion vessel 12 provides the toilet B with filtrate by means of a three-way valve 13 which selectively connects the toilet B to the expansion vessel 12 or the on-board water tank D. In other words, this valve 13 is capable of supplying the toilet B with clean water, stored in the on-board water tank D, via the conduit L7 when the recycling device C is malfunctioning for example.

Furthermore, the recycling unit C implements a non-return clack valve 15 between the on-board water tank D and the expansion vessel 12 aimed at preventing the return of water filtered by the ultrafiltration module 8 towards the on-board water tank D via the conduit L7 and therefore preventing the contamination of the potable water taken on board the aircraft.

Besides, the recycling unit C implements a back-pressure valve 14 placed on the conduit L5 between the expansion vessel 12 and the grey-water storage tank 2. This valve 14 regularizes the flow rate of the valve 13, i.e. it seeks to improve the precision of dosing of filtered grey water which can be used for washing the toilets and securing the filtrate circuit in preventing any excess pressure in the circuit of the recycling unit C.

The valve 14 is calibrated and adjusted to a value of 50 psi in this example.

Moreover, the recycling unit C is connected to a control and command device E, or overall supervision unit, which takes the form of an electronic controller capable of executing a software application, or computer program for processing signals to measure and command the recycling unit C according to the measurement signals. An electronic controller E of this kind thus receives data measured by the level sensor 3, the flowmeter 6 and the pressure sensors 7 and 9 in particular, and is capable of activating the transmembrane high-pressure alarm mentioned here above. This electronic controller E is furthermore capable of delivering command signals to the valves 1, 10, 11, 13 and 14.

All the information on the working of the recycling unit C and especially the flow of water to be processed, the level of the tank 2, the pressure in the conduits and the difference of pressure can be stored in an electronic storage memory of the electronic circuit E (and/or in chips for example, the memory of which is read when the aircraft is on the ground) for example. This information is available in real time in order to enable easier maintenance when the aircraft has landed and is on the ground.

In other words, the clock, alarm and command signals of the recycling unit C are managed by the electronic controller E which furthermore makes it possible to supervise the state of the system.

Here below, a description is given of the different modes of operation of the recycling device C of the invention which are commanded by the electronic controller E.

Production Mode

In this mode of operation, the recycling unit C is active. The wastewater from the basin A flows by gravity into the reception vessel 2. The pump 4 then sends wastewater under pressure from the vessel 2 to the ultrafiltration module 8.

The filtrate is then stored in the expansion vessel 12 until the next flushing while the concentrate, held by the ultrafiltration module 8, is discharged by means of the discharge valve 11 towards the drainmast by the conduit L8.

During a flushing operation, a part of the filtrate (about 200 milliliters) stored in the expansion vessel 12 is sent, by pressure contained in the expansion vessel 12, to a toilet B by means of the valve 13 so as to flush the bowl.

The back-pressure valve 14 then plays its role of regulating the flow rate of the water sent into the toilet B and of keeping the pressure in the circuit of the recycling unit C.

The expansion vessel 12 is connected to the ultrafiltrate circuit under pressure and gets filled when the pressure rises in the circuit. Once the pressure reaches the calibrated back-pressure value of the valve 14, it opens to discharge the filtered water into the vessel 2 for collecting grey water. The pressure of the ultrafiltrate circuit then falls back and the back-pressure valve 14 closes and so on and so forth.

When a flush-pulling operation is activated in the toilet B, the valve 13 opens and recycled water is sent to the toilet B.

It must be noted that the pressure of the ultrafiltrate circuit would fall very quickly if there had been no expansion vessel 12. The expansion vessel 12 makes it possible to maintain the pressure in a system (in this case that of the ultrafiltrate) even if it loses water (within certain limits naturally).

The expansion vessel 12 is herein constituted by a flexible pouch (made of rubber) into which the water enters. This flexible pouch is surrounded by gas (nitrogen for example) at a determined pressure. When the pouch is emptied, the gas keeps the residual liquid at the initial pressure.

In this mode, the wastewater stored in the vessel 2 is thus processed in batches and the concentrate retained by the ultrafiltration module 8 is sent out to drainage either upon a clock signal or upon a transmembrane high-pressure signal.

Emptying Mode

When the aircraft is on the ground, it is possible to empty out the entire recycling unit C (tanks and circuits) as well as the drainmast (this is the emptying mode).

The emptying of the recycling unit C is activated upon a landing signal or a aircraft door-opening signal given by the aircraft electrical system to the electronic controller E of the recycling unit C.

So long as the electrical supply of the aircraft is maintained, the emptying of the unit C is activated. In this case, the pump 4 is activated (in operation) and the drainmast is opened.

The access to the reservoir or vessel 2 is prevented by the valve 1, i.e. the wastewater flowing from the wash-basin A is directed directly to the drainmast via the conduit L9.

When the sensor 3 of the level of the vessel 2 detects the fact that the vessel 2 is empty, the pump 4 stops and the drain valve 10 remains open.

The drain valve 10 is open by default, which means that the recycling unit C can finish getting drained even when the electrical supply of the aircraft is cut off (when it is put in the hangar).

Backwashing Mode

The backwashing mode consists in backwashing a filter in order to remove the particles that have accumulated therein and in order to prevent the filter from getting clogged. In the context of the invention, backwashing is applied to the filter of the ultrafiltration module 8 and makes it possible to avoid a chemical washing of this filter.

Backwashing can, for example, be triggered upon an alarm indicating transmembrane high pressure of the filter measured by the pressure sensors 7 and 9 or/or be triggered upon a clock signal.

To carry out this backwashing, the pump 4 is stopped and the valve 4 for discharging concentrates to the drain is opened.

The backwashing is done by sending filtered water (stored in the expansion vessel 12) in a counter-flow into the ultrafiltration module 8 and then draining it by means of the drain valve 10 which is open.

The concentrates are therefore emptied into the drainmast by the conduit L8. It is then possible to go back to the production mode described here above.

These sequences are managed by the electronic controller E upon a clock signal.

It can therefore be understood that the recycling unit E can be used in the backwash mode to try and restore appropriate pressure to the ultrafiltration module 8. If this operation is unsuccessful, then it is necessary to wait for the aircraft to land and for a maintenance operation to be performed by an operator.

Bypass Mode

If there is clogging of the membrane of the filter used in the ultrafiltration module 8 (i.e. when the transmembrane pressure cannot get stabilized at an appropriate level), then the recycling unit C can be deactivated and bypassed in order to return to a classic functioning of the toilet B, the flush system of which is then supplied with water by the on-board water tank D via the conduit L7.

In this case, the wastewater from the wash-basin A flows directly into the drainmast via the conduit L9 and the flushing of the bowl of the toilet B is then done by the on-board potable water system (the toilet B thus remains functional).

It is possible during this mode of operation to purge the recycling unit C by a backwash as described here above.

Other Aspects and Variants

Unlike in the prior-art known devices, the recycling unit C is relatively light. Its weight does not exceed 6 kg, the supporting elements included. It is preferably made out of plastic.

In particular, because of the low pressures implemented, the casing of the ultrafiltration module is thin and light.

Besides, the recycling unit C is placed under the wash-basin A of the toilet module and is therefore easily accessible.

The recycling unit C is fixed reversibly to the toilet module by winged screws or the like, thus enabling easy and fast dismantling by hand.

Besides, the hydraulic connection systems can be mounted and dismantled by hand.

It can be noted that with a view to compactness, the general shape of the recycling unit C is dedicated to the toilet module. Thus, the elements are specifically molded to adapt to the geometrical constraints of the toilet module.

Besides, the maintenance of the recycling system C is facilitated. In the event of clogging, the ultrafiltration module 8 is easily replaceable. Alternatively, the recycling unit C can easily be replaced, without any tools, within approximately 15 minutes. These actions are then done during the maintenance phases when the aircraft is on the ground.

In both cases, no tools are needed. Indeed, the elements are locked into the recycling unit C.

In addition, in the event of any presence of signs of color in the water, it possible if necessary to add an activated carbon filtering cartridge into the recycling unit C.

Thus, the device of the invention is aimed at recycling grey water from a transportation vehicle to use it as a cleaning/flushing fluid for cleaning and flushing a toilet bowl or even several toilet bowls.

The implementation of such a device simplifies the operations of maintenance, reduces manufacturing costs and improves safety by reducing the number of constituent elements to the minimum.

It must be noted that the device is also adapted to recycling grey water from a shower towards the toilets of a transportation vehicle.

Naturally, the invention is not limited to the example that has just been given and many improvements can be made to this example without departing from the framework of the invention. 

1. Device for recycling grey water, particularly for a transportation vehicle equipped with a tank of clean on-board water, said device being intended for providing recycled water for the emptying of at least one toilet mounted in said vehicle, said device comprising a vessel for collecting grey water, a pump to make at least at a part of the grey water stored in the vessel circulate towards filtering means and a tank for storing filtered grey water useable for washing the toilets, said filtered grey water being stored under pressure in said tank, characterized in that said filtering means comprise an ultrafilter.
 2. Device for recycling according to claim 1, characterized in that said filtered grey water is stored in said tank at a pressure of 2 to 4 bars.
 3. Device for recycling according to claim 1, characterized in that it comprises means for reversible fastening to a toilet module comprising a wash-basin and a toilet.
 4. Device for recycling according to claim 1, characterized in that it comprises a valve to selectively connect said toilet to the filtered grey-water storage tank or to said clean on-board water tank.
 5. Device for recycling according to claim 4, characterized in that it comprises a non-return clack valve between said clean on-board water tank and said valve.
 6. Device for recycling according to claim 4, characterized in that it comprises a back-pressure valve between said valve and said vessel for collecting grey water.
 7. Device for recycling according to claim 1, characterized in that said device for recycling comprises pressure sensors placed respectively upstream and downstream to the filtering means so as to determine the difference in pressure between the inlet and the outlet of the filtering means.
 8. Device for recycling according to claim 1, characterized in that it comprises a sensor for sensing of grey water in the vessel.
 9. Device for recycling according to claim 1, characterized in that it is connected to electronic control and command means.
 10. Device for recycling according to claim 9, characterized in that said electronic control and command means comprise means commanding the starting or stopping of said recycling device.
 11. Device for recycling according to claim 9, characterized in that said electronic control and command means include means commanding the back-washing of the filtering means with filtered grey water stored in said tank.
 12. Device for recycling according to claim 11 characterized in that, to command the backwashing of the filtering means, said electronic control and command means take account of at least one of the following criteria: a predetermined duration of operation of the filtering means; a predetermined loss of load through the filtering means; a volume of water filtered by the filtering means; a clock signal; output signals from the pressure sensors; a water flow-rate signal.
 13. Device for recycling according to claim 10, characterized in said electronic control and command means include means commanding the emptying of said recycling device and implementing said pump.
 14. Device for recycling according to claim 10, characterized in that said electronic control and command means include means commanding the draining of the matter in suspension from the grey water retained by the filtering means.
 15. Device for recycling according to claim 1, characterized in that it comprises means for linking the vessel for collecting grey water to a wash-basin or to a shower mounted in said vehicle.
 16. A transportation device comprising: a toilet included on the transportation device; a grey water source provided on the transportation device; a tank for receiving and holding grey water disposed on the transportation device; a membrane separation unit for filtering the grey water produced on the transportation device; a pump for pumping grey water from the tank to the membrane separation unit; wherein the membrane separation unit filters the grey water and produces a filtrate and a concentrated stream having matter removed from the grey water; a pressure vessel located downstream from the membrane separation unit for receiving filtrate produced by the membrane separation unit and holding the filtrate under pressure greater than atmospheric pressure; and a flush line operatively interconnected between the pressure vessel and the toilet for directing filtrate stored in the pressure vessel to the toilet for flushing the toilet.
 17. The transportation device of claim 16 wherein the membrane separation unit includes an ultrafiltration membrane.
 18. The transportation device of claim 16 wherein there is provided a flush control valve in the flush line for controlling the flow of filtrate into the toilet; and wherein there is provided a back pressure valve operatively associated with the flush control valve for regulating the flow of filtrate through the flush control valve into the toilet.
 19. The transportation device of claim 18 wherein there is provided a recycle line operatively interconnected between the pressure vessel and the tank that receives and holds the grey water, and wherein the back pressure valve is operatively connected in the recycle line.
 20. A method of conserving and managing water used on an airplane, comprising: directing potable water to units on the airplane that produce grey water and producing grey water; storing the grey water in a grey water tank on the airplane; pumping the grey water from the grey water tank to a membrane separation unit and filtering the grey water with the membrane separation unit to produce a filtrate and a concentrated grey water stream; directing the filtrate from the membrane separation unit to a pressure vessel located on the airplane downstream of the membrane separation unit; maintaining the filtrate in the pressure vessel at a pressure greater than atmospheric pressure; and selectively directing filtrate in the pressure vessel to a toilet located on the airplane and utilizing the filtrate produced by the membrane separation unit to flush the toilet.
 21. The method of claim 20 wherein the membrane separation unit includes an ultrafiltration membrane.
 22. The method of claim 20 including utilizing a back pressure valve to control the flow of filtrate from the pressure vessel to the toilet.
 23. The method of claim 20 including maintaining the pressure in the pressure vessel at 2 to 4 bars.
 24. The transportation device of claim 16 wherein the transportation device is an airplane having the toilet, tank, membrane separation unit, pump and pressure vessel disposed thereon. 